The answer, or at least an important part of it, is as simple (and complicated) as this: children with ASD may not derive pleasure from social interaction. That much might be surmised by the parents of such children, based on their behavior, but Dr. Malenka and colleagues are discovering what is happening in the brain so that no pleasure is felt. They hope this work will lead to future new treatments to improve social engagement and enjoyment for these children.

As reported on September 12th in the journal Nature, Dr. Malenka and team conducted experiments in animal models and found that an important hormone, called oxytocin, must act in concert with the neurotransmitter serotonin in a part of the brain called the nucleus accumbens (NA) to generate the “pleasure” that normally occurs during social interactions. The pleasurable sensation elicited by this process is normally felt when engaging in a variety of social activities ranging from bonding with one’s parents to spending time with friends to mating and sexual behaviors. The pleasure experienced is typically self-reinforcing―once enjoyed, pleasurable social contact is desired, and sought out.

Dr. Malenka’s team performed genetic experiments in mice that effectively blocked the oxytocin-induced social reinforcement signal. The resulting behavior of the mice was analogous to that of children with ASD: they did not seem to get any pleasure from interacting with their playmates. Through the successful blockage, they proved, for the first time, that receptor “ports” for oxytocin are present in reward centers of the brain, and specifically the NA.

“People with autism spectrum disorders may not experience the normal reward the rest of us all get from being with our friends,” Dr. Malenka told Time magazine. “Our results,” he added, “suggest that maybe combining oxytocin with a serotonin drug might be beneficial.” The most commonly prescribed antidepressant medications, the class of drugs like Prozac called SSRIs (selective serotonin reuptake inhibitors), act to boost available serotonin levels between brain cells.